During investigative and surgical procedures, in particular endoscopic procedures, a bite block is typically inserted within the patient's mouth so as to maintain the teeth in a spaced apart relationship so as to allow the introduction of a medical device within the oral cavity of the patient. The bite block prevents the patient from biting upon the medical instrument thus protecting the instrument and preventing the patient's teeth being damaged by the instrument. U.S. Pat. No. 4,604,2783 (Green et al.) discloses a device having an annular body which is sufficiently rigid to resist compression and is provided with a relatively soft outer layer to cushion the patient's bite. Bite blocks such as those disclosed by Green et al. are typically annular or tubular in shape and are used to maintain the upper and lower teeth of a patient in a spaced apart relationship by contacting predominantly the incisor teeth of the patient.
Although such bite blocks protect the patient and medical device, patients undergoing endoscopic procedures whilst under sedation are often observed to undergo hypoxia, that is, the fall of oxygen saturation in the blood below acceptable levels. The degree of hypoxia may be minor which is considered tolerable in younger patients. However, the effects of hypoxia can be more serious and, particular with elderly patients and patients with respiratory and/or cardiovascular disorders, can be dangerous or injurious to health. In such patients, the degree of hypoxia induced by sedation and the obstruction to the airways caused by a bite block and endoscopic instruments, has been known to precipitate cardiac or respiratory arrest. Furthermore, patients suffering from the effects of hypoxia have been observed to recover more slowly from sedation and/or anesthesia and may as a result suffer post-operative complications requiring additional care.
U.S. Pat. No. 5,273,032 (Borody), an earlier patent to the present inventor, describes a bite block which includes integral passages directed at a patient's nostrils from below and internally into the patient's oral cavity when in use. The device includes an inlet for the introduction of oxygen into the integral passages so as to allow continuous insufflation of oxygen during use so as to maintain patient vascular oxygenation.
Another device for oxygenating the oral cavity of a patient is described in U.S. Pat. No. 5,413,095 (Weaver) whereby oxygenation to the patient is achieved by a bite block having two parallel channels formed in the bite block and exiting into the mouth of the patient, the channels being formed to receive a pair of nasal cannulae which extend from a common oxygen supply or a single adapter extending from an oxygen supply tube, so that all oxygen is supplied directly and exclusively to the mouth of the patient.
A further device is described in U.S. Pat. No. 5,513,634 (Jackson), whereby a standard bite block is described to which a manifold having flexible oxygenating nasal prongs is attached, the nasal prongs extending upwards from the manifold into the patient's nostrils to supply supplementary oxygen rich gas to the patient which is separate from the air breathed through the patient's mouth. Nasal prongs of this type have however been found to cause the patient discomfort.
Other disadvantages and shortcomings of prior art tubular bite blocks include concentrated loading to the incisor teeth which may cause damage to the teeth due to increased stresses both during endoscopy and during removal of the bite block. Also, devices which deliver oxygen only to the nasal passages of a patient can cause patients to develop nose bleeds due to dryness caused to the nasal canal. Furthermore, a significant portion of patients do not breathe nasally during or after endoscopic procedures for a variety of physical or physiological reasons and as such, can be deprived of oxygen.
A further and recurrent problem with bite blocks of the prior art is the rather small oral opening provided through the bite block which does not allow the introduction of a large dilator such as a Fr 60, which has a diameter of 20 mm. During a dilation procedure in which a large dilator is to be used, the bite block must first be removed from the patient and an alternate obturator, such as a large syringe, must be inserted prior to the dilation procedure taking place.
Any discussion of documents, publications, acts, devices, substances, articles, materials or the like which is included in the present specification has been done so for the sole purpose so as to provide a contextual basis for the present invention. Any such discussions are not to be understood as admission of subject matter which forms the prior art base portion, or any part of the common general knowledge of the relevant technical field in relation to the technical field of the present invention to which it extended at the priority date or dates of the present invention.